F-tilt can be punished on block pretty easily if Ike doesn't have optimal spacing (or PSed, since it's slow enough). And it's pretty laggy. F-air is not as laggy, but same story goes for it if Ike doesn't have optimal spacing. And it's also slow enough for a rather easy PS.
F-smash can be camped, and the ending lag is large enough to be punished in other ways so who the **** cares if it pushes away people 90 miles.
Jab is punished by Up-B.
If you do any other aerials, special moves, those get punished on block by Up-smash or by other dumb crap. Quick Draw fully charged has good shield pushback, but is so massively laggy that a reverse F-smash punishes it out of shield.
Mario basically can easily punish Ike's entire moveset on block. You can't really do anything fancy in this matchup, and anything that somehow isn't punishable on block, I could be camping out anyway. And as I was saying, if you're gonna whine that fireballs aren't a big deal because you can easily PS them, Ike's F-air is also an easy PS, and in that case a free F-smash for Mario.
All this especially matters when Mario lands hits or throws you upwards, since basically Ike is more or less helpless once he's tossed in the air. Especially on FD, you're more or less screwed if you do any attacks while coming down and the Mario doesn't suck at reacting. Pretty much all of Ike's aerials are blockable on reaction. Ike is pretty slow in the air, so it's not hard for Mario to chase and stay under him and then shield -> Up-smash whatever Ike does (including F-air). If Ike air dodges, that can be rather easily punished with grabs or D-air, both of which restart the situation for Ike again.
Right, so I'll expect you're gonna tell me something about Ike landing random Up-airs from his Up-throw...but he's significantly slower and more telegraphed, and the option of edgeguarding if Mario DIs towards the ledge isn't nearly as viable for him.
The one thing you can be glad about: Mario doesn't have very good grab range, so there is a bit more room for error on his part when throw juggling Ike. Of course, you gotta watch yourselves against a guy like ROB...who can easily win this matchup with just grabs. =/